1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor devices and, more particularly, to cleaning semiconductor substrates.
2. Description of the Related Art
As is well known to those skilled in the art, the fabrication of semiconductor devices involves numerous processing operations. These operations include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography patterning, etching operations, chemical mechanical polishing (CMP), etc. Typically, these operations generate contaminants such as particles and residue, which are adhered or absorbed by the wafer surfaces. It is well established that contaminants should be removed from wafer surfaces, as the existence of such contaminants has detrimental effects on the performance of the integrated circuit devices. To achieve this task, wafer surfaces are cleaned as a result of which contaminants such as adhered particles and absorbed compounds (e.g., chemicals) are removed from wafer surfaces.
Normally, double-sided cleaning processing tools are implemented to clean wafer surfaces. FIG. 1 illustrates a cross sectional view of a double-sided horizontal wafer scrubber 100 designed to clean a top surface and bottom surface of a wafer 102, in accordance with the prior art. As shown, the wafer scrubber 100 includes a top brush 104a and a bottom brush 104b, each mounted on a corresponding brush core 106a and bottom brush core 106b. Each of the top brush core 106a and the bottom brush core 106b includes a top shaft 108a and a bottom shaft 108b, each connected to a fluid inlet (not shown in FIG. 1). As shown, the outer surface of top and bottom brushes 104a and 104b are covered with a plurality of nodules 104a and 105b, respectively.
The wafer 102 is shown to be engaged by a pair of rollers 114a and 114b. As can be seen, the wafer 102 is held horizontally by the pair of rollers 114a and 114b and top and bottom brushes 104a and 104b. Top and bottom surfaces of the wafer 102 are scrubbed, respectively, by top and bottom brushes 104a and 104b, which rotate in top and bottom brush rotation directions 110a and 110b, correspondingly. The rollers 114a and 114b rotate while holding the wafer 102, causing the wafer 102 to rotate. The wafer 102 is cleaned as top and bottom brushes 104a and 104b come in contact with top and bottom surfaces of the wafer 102, removing the contaminants.
Normally, each brush core 108a and 108b is connected to a respective fluid inlet designed to supply fluid into the brush cores 108a and 108b. Although not shown, each top and bottom brush core 106a and 106b has a plurality of holes thereon allowing fluid to exit top and bottom brush cores 106a and 106b so as to flush top and bottom brushes 104a and 104b, respectively.
To scrub and rinse wafer top and bottom surfaces thoroughly so as to remove any remaining contaminants, chemicals are initially supplied through the brush (TTB), saturating top and bottom brushes 104a and 104b. Wafer top and bottom surfaces are then scrubbed by top and bottom brushes 104a and 104b for a desired time. Then, top and bottom surfaces of the wafer 102 are rinsed TTB. That is, top and bottom brushes 104a and 104b are flushed and saturated with DI water so as to eliminate scrubbing chemicals in top and bottom brushes 104a and 104b as well as disposing of any contaminant remaining on top and bottom surfaces of the wafer 102. The rinse operation thereafter continues until any and all contaminants remaining on top and bottom surfaces of the wafer have been removed. At this point, the cleaned wafer is removed from the brush scrubber 100, allowing the next wafer to be placed on the rollers 114a and 114b. In this fashion, each wafer is scrubbed and rinsed in the prior art brush scrubber 100.
Repeatedly flushing top and bottom brushes 104a and 104b with chemicals followed by rinsing of the chemicals out of top and bottom brushes 104a and 104b using de-ionized water is not without negative consequences. For instance, a significant amount of chemicals is wasted during each and every brush scrubbing operation. The brushes arc saturated with chemicals to perform the scrubbing operation. Immediately thereafter the brushes are rinsed with DI water, ultimately resulting in wasting a substantial amount of chemicals, overall. In addition to wasting chemicals, the pH of top and bottom brushes 104a and 104b is repeatedly and constantly oscillating, undesirably creating a constant non-equilibrium in top and bottom brushes 104a and 104b. 
Another negative effect of TTB scrubbing and rinse operation is reintroduction of contaminants onto the wafer top and bottom surfaces. For instance, residues remaining in top and bottom brushes are re-introduced into the rinsing interface by the rinse fluid applied TTB. Additionally, chemicals in top brush drip on to the top surface of the wafer, recontaminating the wafer top surface having the active components, damaging the wafers and significantly reduce wafer throughput.
In view of the foregoing, there is a need for an improved semiconductor processing apparatus and methodology capable of minimizing wasting of chemicals during cleaning operation while increasing wafer throughput through preventing recontamination of wafer surfaces.
Broadly speaking, the present invention fills these needs by providing an apparatus and methodology capable of substantially minimizing fluids used during substrate cleaning operations while increasing wafer throughput. In one embodiment, top and bottom surfaces of the wafers are cleaned in a brush scrubber-rinse module. In one embodiment, top and bottom brushes of the brush scrubber-rinse module saturated with scrubbing fluid are implemented to scrub wafer top and bottom surfaces through the brush (TTB). Top and bottom brushes are squeezed, eliminating excess scrubbing fluid. Top and bottom surfaces of the wafer are then rinsed using a rinse fluid introduced onto the wafer top and bottom surfaces through respective rinse nozzles.
It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a method for cleaning top and bottom surfaces of a semiconductor substrate is provided. The method includes scrubbing a top surface of the semiconductor wafer with a top brush and a bottom surface of the semiconductor substrate with a bottom brush. The top brush and the bottom brush are saturated and supplied with a scrubbing fluid. The method also includes squeezing the top brush and the bottom brush so as to press out excess scrubbing fluid by continuing to apply the top brush against the top surface and the bottom brush against the bottom surface of the semiconductor substrate, but without supplying the scrubbing fluid. The method further includes moving the top brush away from the top surface of the semiconductor substrate and the bottom brush from the bottom surface of the semiconductor substrate. Also included is rotating the top brush to prevent dripping onto the top surface of the semiconductor substrate. The method also includes rinsing the top and bottom surfaces of the semiconductor substrate using a rinse fluid while continuing to rotate the top brush that was squeezed to press out the excess scrubbing fluid.
In another embodiment, a method for cleaning a semiconductor substrate is provided. The method includes scrubbing a top surface of the semiconductor substrate with a top brush and a bottom surface of the semiconductor substrate with a bottom brush. The top brush and the bottom brush are saturated with a scrubbing fluid. Also included is squeezing the top brush and the bottom brush so as to press out excess scrubbing fluid. The method further includes moving the top brush away from the top surface of the semiconductor substrate and the bottom brush from the bottom surface of the semiconductor substrate while rotating the top brush. Further included in the method is rinsing top and bottom surfaces of the semiconductor substrate using a rinse fluid.
In yet another embodiment, a method for cleaning top and bottom surfaces of a semiconductor substrate is provided. The method includes scrubbing a top surface of the semiconductor substrate with a top brush and a bottom surface of the semiconductor substrate with a bottom brush. The top brush and the bottom brush are saturated and supplied with a scrubbing fluid. The method also includes squeezing the top brush and the bottom brush so as to press out excess scrubbing fluid by continuing to apply the top brush against the top surface and the bottom brush against the bottom surface of the semiconductor substrate, but without supplying the scrubbing fluid. Also included in the method is moving the top brush to a side of the top surface of the semiconductor substrate and moving the bottom brush away from the bottom surface of the semiconductor substrate to prevent dripping onto the top surface of the semiconductor substrate. Also included is rinsing the top and bottom surfaces of the semiconductor substrate using a rinse fluid.
In still a further embodiment, a method for cleaning top and bottom surfaces of a semiconductor substrate is provided. The method includes scrubbing a top surface of the semiconductor wafer with a top brush and a bottom surface of the semiconductor substrate with a bottom brush. The top brush and the bottom brush are saturated with a scrubbing fluid. The method also includes squeezing the top brush and the bottom brush so as to press out excess scrubbing fluid. Also included is moving the top brush away from the top surface of the semiconductor substrate and the bottom brush from the bottom surface of the semiconductor substrate while rotating the top brush. Further included in the method is rinsing the top and bottom surfaces of the semiconductor substrate using a rinse fluid.
The advantages of the present invention are numerous. Most notably, in contrast to the double-sided wafer scrubbers of the prior art in which cleaning fluid and rinsing fluid are introduced into the cleaning interface through the brush (TTB), the embodiment of the present invention introduce scrubbing fluid to the cleaning interface TTB during the scrubbing operation. However, top and bottom surfaces of the wafer are rinsed using rinse fluid delivered onto the wafer surfaces using rinse nozzles. In this manner, there is substantially no need to flush out the scrubbing fluid in the brushes before performing the rinse operation. Another advantage of the embodiments of the present invention is that the concentration of scrubbing chemicals in the brushes are remained substantially constant. Still another advantage of the present invention is that the overall use of chemicals during the cleaning operation is substantially reduced. Yet another advantage of the embodiments of the present invention is that the scrubbing and rinse operations are performed in a single module. Still another advantage is that the embodiments of the present invention substantially eliminate the possibility of recontamination of the wafer surfaces through dripping of scrubbing liquid. Yet another advantage is that the embodiments of the present invention substantially prevent introduction of contaminants remaining in the brushes onto the wafer surfaces.